Hi. My name is Gloria Casas, and today I'm going to talk about the effect of particle size of soy protein concentrate on amino acid digestibility and concentration of metabolizable energy, and the effect of inclusion of soy protein concentrate on growth performance of weanling pigs.

For that, I'm going to describe three different experiments: the first one about amino acid digestibility, the second about the energy digestibility, and the third one about the growth performance.

Previous research has demonstrated that reduction of particle size can increase the digestibility of nutrients in some ingredients. In 2003, Fastinger and Mahan demonstrated that decreasing the particle size can increase the standardized ileal digestibility values of most of the amino acids in soybean meal. Later, in 2015, Rojas and Stein demonstrated that decreasing the particle size of corn can increase the concentration of digestible and metabolizable energy.

For this particular experiment, we have a batch of soy protein concentrate ground at 700 microns. This batch was divided in three different parts, and two of these parts were processed by micronization: one part, to obtain a particle size of 70 microns that I will call in this presentation SPC-70; the second part was ground at 180 microns and I will call it SPC-180. The third part was kept in the same particle size of the original batch. With these three sources, we conducted the first two experiments.

The first experiment was about amino acid digestibility. In this experiment, we determined the standardized ileal digestibility of crude protein and amino acids on soy protein concentrate ground at three different particle sizes.

In this experiment, we had six pigs of 12 kg of body weight that were installed with a T-cannula in the distal ileum. These six pigs were allotted to six different experimental diets. The diets consisted in one diet containing soybean meal, three different diets containing the sources of soy protein concentrate, and one diet containing fish meal as the only source of amino acids. And one additional diet was formulated as a nitrogen free diet that was used to calculate the endogenous losses. This experiment was conducted in six periods.

Results of this experiment indicate that there were no difference among the ingredients on SID value of most of the dispensable and indispensable amino acids. This graph shows the SID value for the limiting amino acids: lysine, methionine, threonine, and tryptophan. We didn't observe difference among the ingredients on SID values of lysine, methionine, and threonine. But for tryptophan, the SID in SPC-180 was greater than in SPC-700 and soybean meal, but not different than the values for fish meal or SPC-70.

For the second experiment that was about energy digestibility, we determined the concentration of digestible energy and metabolizable energy in the same sources of soy protein concentrate.

In this experiment, we had 36 pigs of 13 kg of body weight that were allotted to six different diets. The diets consisted in one diet containing just corn as the only source of energy, three diets containing the three sources of soy protein concentrate plus corn as the only sources of energy, one diet containing soybean meal plus corn, and one diet containing corn and fish meal as the only sources of energy. We had six replicates per diet, and the experiment was conducted as a completely randomized design. This experiment was conducted with total collection of fecals using the marker-to-marker approach.

This graph shows the concentration of digestible and metabolizable energy in the ingredients: corn, that is represented by the light blue bar; soybean meal, represented in the dark blue bar; the three sources of soy protein concentrate represented in orange, green, and purple bars; and the values for fish meal that are represented in the red bar. We observed no difference among the ingredients in the concentration of digestible and metabolizable energy.

So far, from these two experiments, we can conclude that were no difference on the SID values between soy protein concentrate ground at 70 microns and soy protein concentrate ground at 180 microns.

And we also observed no difference on the concentration of digestible and metabolizable energy among the three sources of soy protein concentrate.

However, in order to conduct our next experiment, we chose the soy protein concentrate 180 because it shows the better physical characteristics to be included in a complete diet for weanling pigs.

In the growth performance experiment, the objective was to determine the effects on growth performance and blood characteristics of including soy protein concentrate in diets fed to weanling pigs.

For this experiment, we had 160 pigs of 7 kg of body weight that were allotted to four different diets in the Phase 1, and one common diet in the Phase 2. Each phase lasted two weeks. For each treatment, we had eight pens and in each pen, we had five pigs. At the end of Phase 1, we took one blood sample to measure the concentration of TNF-α and immunoglobulin G as an indicator of the immune response. Also, we measured the concentration of Peptide YY, that was an indicator of the homeostasis of energy, and can be related with the feed intake.

Here, we have the experimental diets that contained corn, whey powder, and soybean meal. The control diet contained 5% of fish meal and 5% of plasma. In the second diet, the plasma was replaced by 8% of SPC-180. In the third diet, the fish meal was replaced by 5.25% of SPC-180. And in the fourth diet, both fish meal and plasma were replaced by 13.2% of SPC-180. The inclusion levels of SPC-180 were calculated to obtain the same concentration of digestible lysine that were provided by the fish meal, the plasma, or both of them.

This slide shows the growth performance of the pigs for both phases. The red bar represents the control diet, the orange bar represents the diet that didn't contain plasma, the blue bar represents the diet that didn't contain fish meal, and the green bar represents the values for pigs that were fed diets with SPC-180 but didn't contain plasma or fish meal. We observed no difference among the diets for average daily gain, average daily feed intake, and gain:feed ratio.

In these slides, the colors represent the same diets that they represent in the previous slide. So we can observe that are no difference on the concentration on TNF- α among the treatments, and also were no difference on the concentration of Immunoglobulin G among the treatments. That indicates that the inclusion of soy protein concentrate didn't activate the immune response.

We have here the concentration of peptide YY, and we didn't observe difference among the treatments. That concurs with the lack of difference observed in the average daily feed intake that I showed before.

So in conclusion, from these three experiments, we can say that the particle size did not affect the standardized ileal digestibility of most of the amino acids in soy protein concentrate.

Also, we can say that there are no effects of reduction of particle size on the concentration of digestible and metabolizable energy in soy protein concentrate.

And most importantly, we can say that the soy protein concentrate may replace the plasma and the fish meal in diets for weanling pigs without affecting the growth performance.

I would like to acknowledge Selecta Brazil for supporting this experiment.

And my lab mates from the Stein lab for their help and support.